Research on Overvoltage Suppression Techniques at Motor Terminals in Long-Cable Pulse Width Modulation Drive Systems

In shipboard direct-drive propulsion systems, long cables are typically required to connect the frequency converter to the motor. However, the transmission of high-frequency pulse width modulation (PWM) signals over long cables can induce overvoltage phenomena at the motor terminals, thereby compromising the continuity and safety of the ship's propulsion system. To address this issue, this paper investigates the underlying mechanisms of overvoltage generation at the motor terminals driven by high-frequency PWM over long cables and analyzes the relationship between terminal voltage, terminal impedance, and distributed cable parameters. Furthermore, based on a simulation model of a high-frequency PWM drive system with long cables, this paper explores two passive filter topologies and impedance matching techniques. The proposed approach not only effectively suppresses motor terminal overvoltage but also facilitates the optimization of filter parameters. Simulation results demonstrate that the passive filter design method presented in this paper can significantly mitigate overvoltage.